CULTURE

Not all weeds are unwelcome garden visitors but they do need to be kept under control

Weeds are usually thought of as nasty irritants to be dug out of the ground, cleared from around plants that either we – or those who came before us – have introduced into the garden, but all we are doing as far as nature is concerned is substituting one plant for another; and not always for the good of the ecosystem. Nettles, for example, fix nitrogen in the soil, so although a pest for gardeners, they do have their value. Weeds are also plants that take over a particular area at the expense of other established plants. One of the most persistent of these is the oxalis, which is just losing its tiny yellow flowers and fresh green foliage that carpets the countryside in late winter and early spring. On their own they are a pretty sight covering a hillside or meadow in spring, but in a garden they are «weeds,» choking other plants by stealing nutrients and moisture from the soil, impossible to eradicate totally. While digging them out, one keeps coming across dozens and dozens of tiny bulblets that, if left, will sprout again next season after a long dormancy in summer and fall. Another plant we are seeing more of now in urban gardens is the lantana, which comes in a number of colors that look pretty in pots. However, once planted in a garden it has a tendency to sprawl, filling every available space. The range of naturally occurring plants that one classifies as weeds depends on how natural you want your garden to look, and its proximity to natural landscapes. In the Mediterranean, an area filled with tall leafy stalks of bright yellow daisies now, in May, will bear more resemblance to a dried-out hayfield by June once the temperature rises and moisture is non-existent. But leaving a patch, and watering it, will give you a bright splash of foliage and yellow or white blooms with little effort. The compost heap is the best place for most weeds, but one needs to be sure that none are in flower, otherwise the seeds will lie waiting to germinate wherever you deposit the compost and the problem will begin all over again. Compost heaps can either be a pit dug in the corner of the garden, to fill with slowly rotting cuttings and weeds, or a «bin,» easily constructed from meter-long planks around four posts, leaving the front open or with a couple of removable slats. In some countries small commercial compost bins made of durable plastic are available, but I have not been able to find any in garden stores here this year, although a major foreign hardware chain store reportedly stocked them in the past. Mulch is the best way to prevent unwanted plants from appearing. Any layer of organic matter thick enough (at least 4 or 5 centimeters) to prevent sunlight getting to the soil will stop most growth and any that does get through should be weak enough to be lifted out. Organic mulches include compost, bark, leaves, grass clippings, straw, wood chips, and shredded newspapers, and should be applied after the soil temperature has warmed a bit in spring. Inorganic mulches in use are black plastic sheets under a thick layer of gravel, but you should make sure there is enough moisture in the soil before you lay the plastic, and there should be a slight slope to allow for water runoff. If the area is flat, you will need to punch some tiny holes in the plastic to allow water through, but some weeds (particularly oxalis) will find their way up to any pinprick of light. Not leaving any earth bare between plants will also help. Choose plants that spread out to cover the ground between larger shrubs. A pretty summer-flowering ground cover is Helianthemum (sun rose) that is self-sown, spreading quickly from seed, and its small round blooms come in a variety of colors on a background of tiny grey-green leaves. Its roots spread out to control erosion as well as keep other plants down. Removing weeds It’s better to get weeds out before they are taller than about 6 centimeters (and easily removed using a hand tool) and before they can compete with plants that you want to thrive. Small trowels are best for getting at weeds in your flower beds to avoid disturbing desirable plants. Have a bucket handy to toss the weeds into so that you can dump them on the compost heap as you go, keeping the garden tidy. More convenient, and lighter, than buckets are large rubbery bins that can be squashed into narrow spaces in storage. I found them last year in one major wholesale store, but this year they were not in stock. For larger areas, one way of getting weeds out is by using a hoe with an open stirrup at the end instead of a flat blade, or a diamond or arrowhead shape; both are good for removing small weeds or opening a furrow. Chemical herbicides are as anathema to organic gardeners as damaging to the soil and the general environment when allowed to accumulate over time. A simple way of killing weeds growing in cracks between paving stones is to pour boiling water or vinegar over them; but I have not found that pouring salty water, another «organic» method, on them does much to deter the more pernicious growth. The best weapon against weeds is persistence. Make regular hand-weeding a habit and try and pick them out as soon as they appear to prevent them seeding and to make your job easier, for if you don’t get down to the root they’ll be back in a couple of weeks. Don’t forget that many «weeds» are actually delicacies that add flavor to boiled cultivated greens or in spinach pies. Get an experienced horta gatherer to show you which ones grow in your garden. What some people call a weed can be welcome to another gardener. Some gardening books classify Ornithogalum umbellatum (Star-of-Bethlehem) as a plant to be avoided like the plague, but others recommend it for its white spring flower clusters, although they do warn that it can get out of hand because of its hardy taproot and smaller roots that eventually create taproots of their own. Beware of rooting out seedlings from established desired plants. These can be lifted out and transplanted before they get out of hand. It is said that when a tree is about to die it showers seedlings around it, so beware of weeding too assiduously around favorite plants.